Degradation of malathion and phenthoate by glutathione reductase in wheat germ

Residual malathion in wheat was estimated at a lower value when analysis wa s performed by extraction with acetone after addition of water to swell the wheat, according to the Japanese Bulletin Method. The supernatant of the w heat homogenate showed degradation not only of malathion but also of phenth oate. Malathion and phenthoate were not degraded by the boiled supernatant of the wheat homogenate. It was presumed for this reason that glutathione r eductase (GR; EC 1.6.4.2) in the wheat degraded malathion. The following re sults were obtained: (1) GR originating in wheat could degrade malathion an d phenthoate. (2) The degradation of malathion by the Gn was inhibited by e xcessive GSSG. (3) There was a high correlation between GR activity and mal athion degradation activity of the supernatant of wheat homogenates. It is likely that GR acted on the specific structure of malathion and phenthoate, the S=P-S bond, and the blanch structure bonding with the sulfur atom. Fol lowing the above, extraction with acetone after addition of water (the Japa nese Bulletin Method) should be replaced by extraction with pure organic so lvent and without addition of water for swelling.